Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 171101

Area Forecast Discussion
National Weather Service Sioux Falls SD
501 AM CST Mon Dec 17 2018

.SHORT TERM...(Today and Tonight)
Issued at 231 AM CST Mon Dec 17 2018

The work week starts with much of the same weather-wise as the
past several days. Upper level ridge overhead will continue to
serve up dry and sunny conditions with the main forecast question
pertaining to how warm we get. Models have generally struggled the
past several days with observed high temperatures falling outside
of even the max temperature envelope in some cases. With broad
warm air advection above the surface and sunny skies, expect
today to once again be a mild day for many locations and thus
have continued to lean on the high end of guidance. The caveat
would be south or southeasterly surface winds this afternoon
running over a fetch region that, per latest NOHRSC analysis,
still has a healthy snowpack of as much as 2-6 inches. This may
help to temper the full warming potential from pure mixing,
especially in areas nearest the deepest snow pack. In general,
expect our warmer temperatures to be across our western counties
where upper 40s to even lower 50s are certainly possible while
areas of NW Iowa and SW Minnesota may stay stuck in the upper 30s
to lower 40s.

Tonight, temperatures remain seasonably mild, only falling into the
mid and upper 20s. Can`t completely rule out a bit of patchy river
valley fog with SREF probabilities painting areas west of the
James River where winds are lighter.

.LONG TERM...(Tuesday through Sunday)
Issued at 231 AM CST Mon Dec 17 2018

Tuesday and Wednesday: Weak shortwave sneaks up from the southwest
Tuesday before being overrun by a broader upper level trough for
Wednesday. Operational models and their ensemble members continue to
paint some spotty very light QPF for Wednesday. Forecast
soundings show a pretty good dry layer in the lower levels so not
convinced we see much in the way of measurable precipitation. Have
capped POPs in the slight chance category for now. Will also see
some breezy conditions with this system passage.

Temperature-wise, more favorable westerly flow will keep
temperatures mild for Tuesday and Wednesday, with 925 mb
temperatures warming from the west on Wednesday. Cloud cover won`t
help the warming effort but have still generally leaned toward the
upper bounds of guidance given the trend of the past few days.

Thursday into the Weekend: Upper level ridge rebounds over the
intermountain west by Thursday and slides eastward by Friday. This
will allow our quiet weather to persist into the weekend. Another
disturbance flattens the ridge Saturday but looks to mainly sneak
north of our area. With mid and lower level temperatures a few
degrees cooler, expected afternoon highs from Thursday on to be
cooler than recent reading but still running 5-10 degrees above
their seasonal normals.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 457 AM CST Mon Dec 17 2018

Predominantly VFR conditions expected through the period. Can`t
rule out some patchy fog/low stratus late this evening and
overnight with KHON currently most favored for this potential.
With that said, confidence is too low to include mention at this
time. Additionally, with a strong surface inversion in place,
could see some marginal LLWS overnight as well.




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